Well, while you people seem to love bashing One Piece, you should remember that it is the #1 Shounen Manga in Japan right now, and one of the best-selling series in history.
It might surprise you to know that both One Piece and Dragonball/Z were produced by Toei Animation, and many members of the cast of Dragonball/Z are in One Piece.
Luffy: Tanaka Mayumi (KRILLIN)
Dr. Kureba: Nozawa Masako (GOKU/GOHAN/GOTEN)
Erik The Whirlwind: Nakao Ryuusei (FRIEZA)
There are more examples, but in any case, if you've watched One Piece, you'd know that Luffy on several occasions has dealt with people using energy attacks like 'Kamehameha' and definitely has in-story ways of dealing with them.
The whole argument of "Goku, and (insert other anime character)? No way! Goku would annihilate them!" is ridiculous, because DBZ is so over the top to begin with. How many characters in anime existence could kill Goku? It shouldn't stop interesting games from being made.
If you're not aware, another highly popular game series,
Super Robot Wars Alpha, has gundams/mechs from countless series, and some of them are obviously more powerful than each other, but it doesn't stop EVA-01 from taking on Wing Zero.